KH2PO4 and salicylic acid synergistically promote the germination of rapeseed, Brassica napus, under aluminum stress

Background and aims

Aluminum (Al) toxicity in acid soil has become one of the main stress factors affecting seed germination of crops like rapeseed. Therefore, chemical intervention to alleviate Al stress during rapeseed germination could have a positive effect improving seed germination and promoting strong seedling growth.

Methods

In this study, seeds of the rapeseed cultivar, Zhongshuang 11 (ZS11) were treated with various concentrations of KH₂PO₄ and salicylic acid (SA) during germination, and a quadratic saturation D-optimal regression design was used to derive the optimal concentration for alleviating Al stress (672 μM and 87.5 μM respectively). KH₂PO₄ (KP), SA, and the combination (KP + SA) were applied during rapeseed germination, followed by phenotypic assessment, measurement of physiological indices, and transcriptome sequencing.

Results

The results showed that KP, SA and KP + SA treatments significantly increased the seed vigor and radicle length and reduced the concentration of reactive oxygen species and proline under Al stress. Treatment with KP + SA was significantly more effective than either KP or SA alone. Weighted gene co-expression network analysis identified six differentially expressed genes in the KP + SA treatment group, which could enhance the antioxidant response and Al³⁺ transport in rapeseed radicles through glutathione metabolism, ABC transporters, and other pathways to alleviate Al stress.

Conclusions

The results of this study demonstrate that the synergistic effect of KH₂PO₄ and SA can significantly improve the growth and adaptability of rapeseed seeds in acidic soils, which holds significant importance for agricultural production and soil management.